I’m not sure that was much of an issue for DVD. Historically VHS had those huge licensing terms for new releases ($90 for VHS), but the same rules didn’t apply to DVD (new releases $20). This was one of the main reasons VHS rentals died so fast after DVDs came out.
Also at least at one time, I remember Redbox was simply buying DVDs at retail stores instead of buying from retail stores for their disc inventory. I see that Walmart is listed as a creditor. That makes me think perhaps Redbox still was.